Lithium - serum

Last updated: Tuesday, 30, March, 2004

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Item Process
Specimen

5 mL blood in plain tube; a lithium heparin tube must not be used.

Method

Flame emission spectrophotometry, ISE or spectrophotometry.

Therapeutic Interval
0.6-1.2 mmol/L.
Application

Monitoring lithium therapy, blood should be drawn 8-12 hours after the last dose.

Interpretation

Lithium half-life is 8-20 hours; may be prolonged in renal failure.

Toxic level: >1.9 mmol/L (>1.2 mmol/L may be toxic in older patients).

When levels are >1.5 mmol/L, lithium therapy should be discontinued and the patient assessed for toxic symptoms.

Increased levels may occur in sodium depletion, eg, associated with diuretics.

ReferenceMitchell PB. Br J Clin Pharmacol 2001; 52:1 45-54.